Compression syndromes of the ulnar, median, radial and musculocutaneous nerves have a number of different causes. These lesions often present with vague pain, intermittent sensory symptoms, and occasional weakness. Nerve compression syndromes can be difficult to demonstrate in the office as they often require a specific setting or activity to provoke symptoms (i.e., work, sports).

At the elbow, there is a combination of joint mobility, longitudinal stresses, and fascial restraints that make nerve compression more likely. The lack of bulky muscle and adipose tissue about the elbow makes the nerves vulnerable to direct trauma. The nerves must pass into and around the numerous muscles that originate or insert at the elbow. Anatomic anomalies such as vascular aberrations, abnormal fascial bands, boney prominences, and muscular variants are all well-documented causes of nerve compression.

Athletes and workers that perform heavy and repetitive tasks are at risk for nerve entrapment lesions because the elbow is subjected to intense repetitive muscle actions and large joint forces.

Most of the nerve injuries we see are neuropraxias which are conduction delays with an intact nerve. The prognosis for nerve recovery is usually excellent if proper treatment has been rendered before irreversible damage has occurred.

Direct trauma to a nerve may result in more severe injury in which axon degeneration occurs but the supporting connective tissue sleeve remains intact (axonotmesis). Although the prognosis is good, the time to recovery depends on the distance from the nerve lesion to the site of innervation.

Complete nerve disruption is usually associated with severe fractures, dislocations or deep lacerations and full recovery is unlikely (neurotmesis).

ULNAR NERVE COMPRESSION AT THE ELBOW

Cubital tunnel syndrome

Compression of the ulnar nerve at the elbow is second only to carpal tunnel syndrome as a source of nerve entrapment in the upper extremity. The nerve can become compressed at a number of sites from 10 cm proximal to the elbow to 5 cm below the joint. The most common sites are where the ulnar nerve passes into the groove on the posterior aspect of the aspect of the medial epicondyle, in the cubital tunnel, and where it passes between the humeral and ulnar heads of the flexor carpi ulnaris muscle.

The ulnar nerve is the major nerve about the elbow most susceptible to injury due to compression, traction and repeated irritation. The superficial location of the ulnar nerve at the posteromedial aspect of the elbow contributes to frequent direct trauma. The wide range of motion of the elbow and the stresses applied during the throwing mechanism further contribute to the trauma of the ulnar nerve. In throwing athletes there are significant valgus stresses to the elbow often leading to laxity of the medial collateral ligament. This, in turn, leads to additional traction on the nerve, stretching of the support ligaments and subluxation of the nerve producing fibrosis about the nerve. Chronic symptoms also occur in individuals who put prolonged pressure on the nerve by continuously leaning on the elbow or who keep the nerve on stretch by holding the elbow flexed for long periods during work or recreation. Medial epicondylitis is associated with ulnar nerve compression in 60% of cases. Other causes of ulnar nerve compression are listed below.

Causes of ulnar nerve compression

Compression, traction and repeated irritation

Medial epicondylitis

Throwing, unstable medial elbow ligaments

Racquet sports

Ganglia, lipoma, osteochondroma, osteophytes

Inflamed olecranon bursa

Rheumatoid synovial proliferation

Occupational-related causes: accounts for 30% of cases

Clinical Symptoms

Early symptoms may include paresthesias in the ring and little fingers. Aching in the medial elbow with radiation proximally to the neck or distally may also occur and may extend to the ulnar side of the hand as the condition progresses. The onset may be acute and the result of an injury. More frequently the onset of symptoms is gradual and intermittent. Initially the symptoms may occur with strenuous use of the arm, but later the symptoms become more constant regardless of activity. Patients may report heaviness and clumsiness in the hand and fingers. Cramping with spasm in the ring and little fingers may occur.

Frank weakness cannot usually be demonstrated on physical examination early in the disease. Weakness of the intrinsic muscles is a late finding and can interfere with activities of daily living, such as opening jars or turning a key in a door.

Physical Examination

The physical examination should start at the neck and proceed distally. The physician should palpate along the course of the nerve looking for the following:

Supracondylar bone process

Mass lesion

Hypertrophy of the medial triceps

Cubitus valgus

Evidence of recent of past trauma

Areas of tenderness

A Tinel sign (tapping of the nerve resulting in paresthesias down the arm) is significant only if it is strongly positive. Gentle manipulation of the ulnar nerve behind the medial epicondyle with the elbow flexed 90 degrees may demonstrate subluxation of the elbow and reproduce symptoms.

The elbow flexion test, performed by having the patient flex the elbow while fully extending the writs for 3 minutes, is positive when ulnar nerve symptoms are evoked. There is a high correlation between a positive elbow flexion test and a positive EMG. This test must be carefully interpreted and used in context with other clinical findings since 50% of normal people have similar symptoms with this maneuver.

Sensory changes in the cutaneous distribution of the ulnar nerve should be evaluated with threshold tests of vibration and light touch sensation and monofilament evaluation with Semmes-Weinstein filaments.

Nerve-ending density testing such as two-point discrimination are positive in more advanced disease.

Motor changes are seen earliest in the ulnarly innervated hand intrinsics, as may be determined by the finger-crossing test (crossing the index and middle fingers). Loss of pinch strength and Froment sign signal adductor pollicis weakness. Loss of adduction weakness ability by the little finger may be apparent on testing.

More advanced compression may produce flexor digitorum profundus asthenia in the little and ring fingers and possibly flexor carpi ulnaris weakness. Frank atrophy is a late finding and has a poor prognosis. Clawing may be evident if intrinsic wasting precedes FDP involvement.

Assessment must include evaluation for medial epicondylitis and elbow medial collateral ligament laxity. Subtle instability may be detected by comparing both elbows.

Differential Diagnosis

Cervical root compression (C8)

Osteophytes seen on x-ray

Herniated cervical disk: Check reflexes

Pancoast tumor: CXR

Thoracic outlet syndrome:Normal EMG

Carpal tunnel syndrome

Numbness in thumb, index, and middle finger

Thenar atrophy

Medial Epicondylitis

Tenderness over medial epicondyle

No distal weakness, paresthesias or numbness

Ulnar nerve entrapment at wrist

Strong wrist flexors and ulnar deviators

Sensation intact over dorsomedial hand and dorsum of little and ring fingers

Medical causes of nerve dysfunction

Vitamin B12 deficiency

Folic acid deficiency

Porphyria

Diabetes

Uremia

Alcoholism

Prescription medications

Motor neuron disease

Diagnostic Testing

Radiographic testing is of limited value. X-rays of the cervical spine are valuable when evaluating for cervical spondylosis and uncovertebral spurring. X-rays of the elbow are useful when evaluating for the presence of fracture callus, arthritic spurs, heterotopic bone, and a supracondylar process.

MRI is helpful in evaluating soft-tissue mass lesions or the status of the medial collateral ligament.

Nerve conduction velocity studies provide an objective measurement of nerve compression. A reduction in velocity of 30% or more suggests significant compression of the ulnar nerve. Nerve conduction tests may be negative in mild ulnar nerve entrapment or ulnar neuritis. Even mild compressive neuropathies may significantly compromise work-related and leisure activities.

Overall, the incidence of false negatives in nerve conduction testing is 10%. Many clinicians believe that normal nerve conduction testing should not preclude surgical treatment, nor should they be required for all patients if the remainder of the clinical assessment indicates ulnar nerve compression at the elbow.

Treatment

The treatment of ulnar nerve compression at the elbow depends on the degree of impairment in the nerve.

Conservative treatment

Conservativemeasures consist of rest, anti-inflammatory medication and avoidance of the aggravating activity. Modifying activities in the workplace to limit elbow flexion and direct pressure on the ulnar nerve is the most important step in treatment. At night, an elbow splint that keeps the elbow from flexing to a right angle can be worn. A towel wrapped around the elbow at night can be used. Elbow protection pads used by skaters are available in most sporting goods stores and can be used at night with the padded part of the protector turned so that it is in the antecubital area of the elbow thus preventing elbow flexion.

During the day the sports elbow protector can be used at work to keep from bumping the elbow.

Corticosteroid injections are not recommended.

Surgical Treatment

When conservative management is unsuccessful or if the severity of the ulnar nerve lesion requires operative intervention several options exist. Within our practice, one of three options are used depending on the circumstances of the case.

Medial epicondylectomy requires the excision of the medial epicondyle. By doing so the prominence against which the nerve is compressed is eliminated, and the nerve is free to seek its course of least resistance.

Ulnar nerve transposition requires that the nerve be mobilized to another location anterior to the medial epicondyle. The advantages of this procedure include the repositioning of the ulnar nerve to a bed with less scarring. In addition, the nerve is placed in a new pathway volar to the axis of elbow motion and is functionally lengthened several centimeters. This decreases tension on the nerve with elbow flexion.

The subcutaneous transposition is the procedure of choice during surgical reductions of fractures and dislocations, and replacement arthroplasties of the elbow. It is also preferred in elderly patients with arthritic elbows and in obese patients with thick subcutaneous adipose tissue.

The submuscular transposition ensures that all sites of potential nerve compression are explored and released. Its also relocates the nerve to an unscarred anatomic plane where it is not subject to traction forces. Deep to the entire flexor pronator muscle, it is well protected from compressive forces. The procedure does require more surgical dissection, and postoperative immobilization which may result in flexion contractures.

MEDIAN NERVE COMPRESSION AT THE ELBOW

The median nerve is the least frequently entrapped nerve at the elbow. Throwing and other repetitive tasks involve repetitive forceful gripping, pronation, and sudden extension at the elbow can produce compression at the proximal margin of the pronator teres muscle. Weight lifting may result in building muscle mass and can lead to nerve compression. Trauma to the upper forearm may also result in scarring and can induce compressive neuropathies at the elbow.

The median nerve arises from the nerve roots C6 to T1. After leaving the medial and lateral cords of the brachial plexus it passes down the medial aspect of the arm to the medial humerus. The supracondylar process is a bony projection in this area that may lead to nerve compression. At this level, the ligament of Struthers may result in compression. As the median nerve enters the forearm, it courses under the lacertus fibrosis and then deep to the pronator muscle where compression may occur.

Median nerve compression at the elbow may result in two condition: pronator syndrome and anterior interosseus nerve syndrome.

Pronator Syndrome

Compression of the median nerve in its course about the elbow can be produced by components of the ligament of Struthers, the lacertus fibrosis, the pronator muscle and its fibrous components, and the fibrous proximal margin of the flexor digitorum sublimus muscle.

Pronator syndrome produces symptoms of aching of the volar proximal forearm and distal arm. This aching is aggravated by forceful use of the extremity, especially involving pronation. Sensory loss in the median nerve distribution and weakness or clumsiness are often noted. These symptoms are similar to those seen in carpal tunnel syndrome. In pronator syndrome, night pain is unusual while carpal tunnel syndrome may awaken patients with complaints of aching and numbness in the hands.

Physical Examination

The clinical examination may reveal tenderness of the pronator teres muscle or in the region of the lacertus fibrosis in the proximal ulnar aspect of the volar forearm. A Tinel sign may be present but is often delayed in its appearance.

A supracondylar process, if present, may be palpable.

A Phalen sign (onset of numbness in the distribution of the median nerve in the hand with wrist flexion) is absent. Concomitant carpal tunnel syndrome and pronator syndrome may be present (double-crush phenomenon).

Weakness, if present, may involve the flexor pollicis longus, abductor pollicis brevis, and less often, the opponens and flexor digitorum profundus of the index and long fingers. This may present as complaints of weakness in thumb flexion and pinch strength. Atrophy in the thenar muscles may be noted in advanced cases.

Loss or decreased sensibility on the palmar side of the radial three and one-half fingers may be due to median nerve compression at the carpal tunnel. Loss of sensation in the palmar cutaneous nerve distribution (mid-palm and thenar skin) suggests compression proximal to the carpal canal.

Provocative tests on physical examination can be helpful in eliciting signs of pronator syndrome. Because compression of the median nerve by the lacertus fibrosis is a possibility, hyperflexion of the elbow past 120 degrees with resistant forearm supination may reproduce forearm symptoms if the nerve is compressed by this structure.

Resisted forearm pronation with the elbow flexed followed by elbow extension that increases symptoms suggests the pronator teres as the site of median nerve compression.

Resisted contraction of the long finger flexor digitorum sublimus may elicit symptoms if the long finger FDS is the site of compression.

Diagnostic Testing

Plain x-rays are necessary to rule out a bony supracondylar process in the distal humerus or other post traumatic or degenerative pathology at the elbow as the cause for compression.

Electrodiagnostic studies (EMG/NCS) are rarely diagnostic. They may be helpful in excluding coexisting pathology and may implicate other causes of nerve compression.

Anterior Interosseus Nerve Syndrome

The anterior interosseus nerve is is a division of the median nerve that branches from the median nerve approximately 5 cm below the medial epicondyle. The anterior interosseus nerve then passes behind the median nerve and then through the two heads of the flexor digitorum sublimus muscle.

Because the anterior interosseus nerve has no cutaneous sensory component, numbness is not associated with his syndrome.

Anterior interosseus nerve syndrome includes complaints of absent or decreases function of the flexor pollicis longus, pronator quadratus, and the flexor digitorum profundus of the index finger. This results in weakness or inability to flex the interphalangeal joints of the thumb and index fingers and the patient will be unable to position the thumb and index finger in the shape of a six. A weakened index finger-thumb pinch is noted.

In contrast to pronator syndrome, pain may be elicited by resisted flexion of the flexor digitorum sublimus of the long finger and may also be present at rest and on local palpation of the nerve.

Diagnostic Testing

EMG/NCS may be diagnostic in anterior interosseus nerve syndrome. If the EMG is not diagnostic for anterior interosseus nerve compression, one should consider more proximal causes of nerve compression such as pronator syndrome, brachial plexopathy, or a tendon rupture as occurs in patients with rheumatoid arthritis.

Treatment

The initial treatment for median nerve compression is conservative. Anterior interosseus nerve syndrome usually resolves with time, particularly is the lesion is secondary to neuritis. Observation for 8-12 weeks is favored before surgery is considered. Strengthening of the remaining muscles and modalities such as heat and stretching are useful in most cases.

If no improvement is noted, or if a space occupying lesion is present, surgical release is recommended. Decompression of the median and anterior interosseus nerve, including all suspected sites of compression, is advised.

Postoperatively the elbow is splinted for one week. After this point, flexion and extension exercises are started and slowly progressed.

The prognosis for full recovery is generally very good, provided there is no long standing muscle atrophy before surgery. Full recovery may take as long as 6 months even after surgical decompression. If there is severe nerve damage, recovery may take longer and may be incomplete.

RADIAL NERVE COMPRESSION AT THE ELBOW

One of the more difficult to make diagnoses to make in the upper extremity is distinguishing between radial tunnel syndrome and lateral epicondylitis. Both entities are caused by the same type of problem and may occur consurently in the same patient. The cause is generally related to repetitive and strenuous use of the arm.

The radial nerve is composed of the roots of C6-C8 which form the posterior cord of the brachial plexus. The nerve courses distally along the humerus to the lateral intermuscular septum is found. This is a potential site of compression. The radial nerve then bifurcates into a superficial sensory branch and a deep motor branch (the posterior interosseus nerve) that passes through the radial tunnel.

The radial tunnel is composed of the radiohumeral joint and the superficial head of the supinator muscle where there is a fibrous band known as the arcade of Frohse.

Radial Tunnel Syndrome

The radial tunnel syndrome results from dynamic compression of the posterior interosseus nerve in its course from the anterior capsule of the elbow joint proximally to the arcade of Frohse distally.

Symptoms include deep, dull proximal dorsal forearm ache, often with distal radiation. The pain is often described as a cramp. Night pain is common. Sensory loss over the dorsoradial aspect of the second metacarpal head suggests radial sensory branch involvement. Motor findings are usually absent.

On physical examination, symptoms are aggravated by the following:

resisted supination and extension

resisted extension in the metacarpophalangeal joint of the long finger with the wrist extended

repetitive forearm pronation with the wrist flexed.

Diagnostic Testing

EMG/NCS are not helpful in confirming the diagnosis but may be useful in identifying coexisting pathology.

Injections into the lateral epicondylar area can sometimes help differentiate radial tunnel syndrome from lateral epicondylitis.

Treatment

Conservative treatment is attempted in most cases. Efforts should be made to modify patient activity to avoid provocative positioning of the arm. Ergonomic evaluation should be completed to modify the offending task or job. Task that require elbow extension, forearm pronation and wrist flexion repetitively or for long periods of time contribute to the development of radial tunnel syndrome.

Initial treatment should include rest, stretching and splinting. Corticosteroid injections adjacent to, but not within, the nerve is an acceptable treatment option.

Surgical Treatment

Surgical intervention may be considered if the symptoms are not relieved by rest, activity modification, nonsteroidal anti-inflammatory medication, or a corticosteroid injection. Before considering surgery, precise localization of the pain to the radial tunnel must be confirmed.

Two surgical approaches are acceptable. First, an incision directly over the lateral epicondyle and supinator is considered when the surgeon is certain that the site of compression is the supinator at the Arcade of Frohse.

If doubt exists because of tenderness proximally over the radieal nerve, a more extensile approach is necessary. Care is taken to identify and release all potential sites of radial nerve compression.

Postoperative care involves a bulky long arm dressing to immobilize the elbow for one week. Gradual stretching and strengthening exercises are started at 1 week. Unlimited activities are permitted at 6-12 weeks depending on job requirements.

A gradual return to work program is favored for workers returning to more physically demanding work.

Posterior Interosseus Nerve Syndrome

Posterior interosseus nerve syndrome is a compression neuropathy that presents with weakness or loss of function of the finger and thumb extensors. Conversely, radial tunnel syndrome is associated with pain and little, if any, weakness.

The symptoms may occur after an episode of strenuous arm and/or wrist use involving pronation and supination. Pain at the elbow may precede the weakness, which is usually rapid in progression and may be sequential.

Posterior interosseous nerve syndrome is associated with space occupying lesions such as ganglia. Other possible causes may include synovitis of the elbow joint, and compression by the radial recurrent artery. If compression is secondary to a space occupying lesion, onset may be gradual.

Posterior interossues nerve compression may coexist with lateral epicondylitis. Other potential causes of peripheral neuritis should be considered including polyarteritis and rheumatologic disorders.

Clinically, patients may be unable to extend the finger MP joints or abduct the thumb with the wrist at neutral. Pseudo clawing may be present. The wrist can be actively extended but it usually deviates radially due to weakness of the extensor carpi ulnaris muscle. Radial sensory changes are absent.

Diagnostic Testing

CT scans and MRI may be helpful in identifying space occupying lesions.

EMG’s may be positive after 3 weeks of muscular involvement.

Treatment

Unless space-occupying lesions are identified, open injuries are present, or chronic radial head dislocation is present, conservative management is indicated.

Initial nonoperative treatment should include rest, activity modification, and use of a wrist cock-up splint. A corticosteroid injection should be considered.

If no improvement is seen in 90 days, spontaneous recovery is unlikely, and surgery is recommended.

Sites of Posterior Interosseus Nerve Compression in the Radial Tunnel

Proximal fibrous bands

Fibrous margin of the extensor carpi radialis brevis muscle

Constricting leash of recurrent vessels

Arcade of Frohse

Fibrous bands at distal end of supinator muscle

The operative approach depends on the suspected findings.

If lateral epicondylitis coexists with radial nerve compression at the radial tunnel, the lateral extensor origin and the radial tunnel are released at the same procedure.

An extensive anterior approach is required when complete nerve exploration is indicated.

Postoperative includes early range of motion and progressive strengthening exercises at the wrist and elbow. Early stretches are encouraged to promote nerve gliding.

A gradual return to work and sports activities is expected starting at approximately 6-8 weeks. An earlier return to work may be possible with strict limitations on the use of the postoperative arm.

Summary

In summary, there are a variety of peripheral nerve compression syndromes that are encountered in clinical practice. Not all of these can be easily diagnosed with radiographic or electrodiagnostic studies. An acute awareness of the possible diagnoses is required to make a proper diagnosis and provide appropriate care.